Sealed Wafer Bath Immersion Lithography Fluid Management
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Solution Overview
Problem
Immersion lithography systems face challenges such as fluid temperature control issues, evaporation problems, particle contamination, inconsistent fluid-contact history, and overlay accuracy distortions due to fluid management difficulties in both lens-based (LBC) and wafer-based (WBC) systems, particularly related to edge bead formation and fluid seepage.
Innovation Solution
A full immersion lithography system with a sealed wafer bath using a seal ring and enclosing cover to maintain a fluid-vapor-rich environment, preventing evaporation and particle contamination, and ensuring consistent fluid contact by retaining immersion fluid within a tank between the wafer and lens, with a seal ring and enclosing cover to manage fluid and vapor effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If immersion lithography is performed with liquid filling between wafer and lens, then resolution and depth-of-focus are improved, but fluid temperature control issues and evaporation problems occur
Solution Approach 1:
The system divides the immersion fluid management into separate functional zones: a sealed wafer bath for exposure, a fluid delivery system for temperature control, and a vapor barrier system for evaporation prevention. This segmentation allows independent optimization of each subsystem to address temperature control while maintaining resolution benefits.
Solution Approach 2:
A sealed wafer bath acts as an intermediary container between the immersion fluid delivery system and the exposure field. This sealed environment serves as a buffer that isolates the exposure process from temperature fluctuations and evaporation, while still allowing the immersion fluid to provide its resolution-enhancing optical properties.
2Manufacturing precision
If immersion lithography is performed with liquid filling between wafer and lens, then depth-of-focus is enhanced, but particle contamination occurs
Solution Approach 1:
The sealed wafer bath creates a controlled, particle-free environment for the immersion fluid during exposure. By sealing the fluid within the bath and maintaining it as a separate system from the external environment, particle contamination is prevented while the fluid maintains its optical properties for enhanced depth-of-focus.
Solution Approach 2:
The harmful aspect (particle contamination) is extracted from the immersion fluid system by separating the fluid containment (sealed bath) from the exposure field. The fluid is taken out of direct contact with potential contamination sources while retaining its beneficial optical effects in the controlled bath environment.
3Loss of substance
If fluid is retained within tank between wafer and lens, then evaporation is prevented, but fluid management complexity increases
Solution Approach 1:
The sealed wafer bath merges multiple functions into a single integrated component: it contains the immersion fluid, prevents evaporation, provides thermal isolation, and maintains a particle-free environment. This consolidation reduces the number of separate fluid management components needed, simplifying the overall system despite the added evaporation prevention capability.
4Manufacturing precision
If seal ring and enclosing cover are used to maintain fluid-vapor-rich environment, then overlay accuracy is enhanced, but device complexity increases
Solution Approach 1:
The seal ring and enclosing cover form a flexible sealing system that maintains the fluid-vapor environment without requiring complex rigid structures. The flexible nature of the sealing components allows them to adapt to wafer positioning variations while maintaining overlay accuracy, reducing the complexity compared to rigid sealed systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution prevents water stains, maintains fluid homogeneity, reduces particle generation, and enhances overlay accuracy by minimizing fluid evaporation and turbulence-induced bubbles, ensuring consistent exposure across the wafer surface.
Implementation Method 1
maintain a fluid-vapor-rich environment, preventing evaporation
Implementation Method 2
retaining immersion fluid within a tank between the wafer and lens
Implementation Method 3
preventing evaporation and particle contamination
Data Source
AI summary
Immersion lithography system and method using a sealed wafer bottom are described. One embodiment is an immersion lithography apparatus comprising a lens assembly comprising an imaging lens and a wafer stage for retaining a wafer beneath the lens assembly, the wafer stage comprising a seal ring disposed on a seal ring frame along a top edge of the wafer retained on the wafer stage, the seal ring for sealing a gap between an edge of the wafer and the wafer stage. The embodiment further includes a fluid tank for retaining immersion fluid, the fluid tank situated with respect to the wafer stage for enabling full immersion of the wafer retained on the wafer stage in the immersion fluid and a cover disposed over at least a portion of the fluid tank for providing a temperature-controlled, fluid-rich environment within the fluid tank.